There are 3 numbers on the top of every pole. What do they mean?
-Pole Length
-Weight Rating
-Flex Number
Pole Length:
This is the most straight forward. Some of the shortest poles built for small children are only 8ft long while poles built for Olympians can be 17ft or longer! There is a common tradeoff when choosing which length to use. Shorter poles are typically easier to use while longer poles allow you to vault higher as long as you maintain good technique.
The most common pole lengths are 12ft, 12.5ft, 13ft and 13.5ft. Just these 4 lengths can mostly cover vaulters with PRs within the massive range of 7ft and 14'6. This range of PRs probably covers the wide majority of pole vaulters. Brand new beginners may see faster improvements with poles shorter than 12ft while experienced vaulters will certainly need to move beyond 13.5ft poles.
Pole Weight Rating:
Weight ratings are basically just an easier to use version of flex numbers. These exist to enforce the high school rule: You're not allowed to compete on a pole that 'weighs' less than you weigh. With so many high schools lacking a dedicated pole vault coach, this rule was put in place to limit how often poles break.
In reality, it can be safe to learn how to bend a pole for the first time with a skinny pole under the supervision of an experienced coach. Likewise, experienced vaulters can sometimes generate enough power to snap poles 20lbs over their weight. You always need to pay attention to how much your pole bends and adjust accordingly.
A general rule-of-thumb shorthand that many people in pole vault use is "3 inches of grip = 5lbs of weight." This means that for every 3 inches higher you hold on the pole, it will feel about 5lbs bendier while every 3 inches lower feels about 5lbs stiffer. Likewise, a pole that is a half foot longer, will feel about 10lbs stiffer if you are still holding at the same grip height because you are now 6 inches further down from the top of the pole.
Flex Numbers:
Simply put, the flex number is how many centimeters the pole droops down when you hang a 50lb weight from the middle of it.
Weight ratings have a range of flex numbers associated with them. Because of the way poles are made, it is impossible to guarantee the pole you're making will be exactly the same down to a tenth of a centimeter. So poles that are very similar in bendiness will be grouped into a weight rating. Professional pole vaulters use specific flex numbers almost exclusively because they require those fine tuned details to minimize variables. But until you reach the top level, using weight ratings can make things way easier and pole manufacturers build & sell pole sizes according to the weight label.
It is worth noting, however, that different brands of poles do weight label their poles somewhat differently. A 13' 150 ESSX, 13' 150 UCS and 13' 150 PACER could all have different flex numbers. If you are looking to switch brands, flex numbers can be something you need to consider. Fortunately, the experts here at Pole Vault Mall have a ton of experience with every pole brand out there to help you figure out exactly what you need!